Flashcards
Introduction to Computer Systems: Lecture 8 Operating Systems
Cards in this deck (41)
- 1What is a operating systemA program that acts as an intermediary between a use of a computer and the computer hardware
- 2What is a kernalthe central component of most OS and loads first, controls the system and manages system resources
- 3Name 3 operating system goals• Execute user programs and make solving user problems easier
• Make the computer system convenient to use
• Use the computer hardware in an efficient manner - 4What is the role of OSBridging the hardware/application gap
Resource coordinator (manages resource, prevent improper use)
Facilitator (provides services, libraries, make application programming easier and faster) - 5What is the memory resident componenet in the OSAlways loaded in memory
• Commonly called the kernel
• Contains essential services required by other parts of the
operating system and applications.
• Typically responsible for managing memory, processes and
tasks, and secondary storage - 6What is the memory non resident componentContains infrequetly used programs
Software tools
Terminal commands - 7What is the last component of OSBootstrap program
- 8What is a stand-alone operating system?complete operating system that works on a desktop computer, laptop, notebook computer
DOS, windows 7,8, Unix, Linux - 9What is a server operating system?organizes and coordinates how
multiple users access and share
resources on a network
Windows 2012 server, Unix, Linux, Netware - 10What is a mobile/embedded operating system?resides on a compact ROM or RAM chip on a mobile device or consumer electronic device
Android, iOS, Blackberry - 11What is system calls?computer program requests a service from the kernel of the operating system it is executed on
Written in high-level language (C)
Accessed via Application Program Interface - 12What does the OS do in Kernal mode?The executing code is complete and unrestricted access to the underlying hardware
Can execute any instruction, reference any memory address
Crashes in kernel mode halt entire PC - 13What does the OS do in User Mode?Code has no ability to directly access hardware or memory
Code must use API to access hardware or memory
Crashes are recoverable - 14State some common OS services User interface and command execution
File system management
I/O management
Process management and multi-tasking
CPU Scheduling
Memory management
System protection management and security - 15What is the function of a user interface?controls how you enter data/instructions
and how information is displayed on the screen - 16State the 3 types of user interfacesGUI - Graphical User Interface
• CLI - Command Line Interface
• TUI –Text-based User Interface - 17What does a basic file management system provide?•Directory structures for each I/O device
• Tools to copy, move, store, retrieve and manipulate files
• Information about each file in the system and the tools to access
that information
• Security mechanisms to protects files and control access
•Backup & file compression - 18What happens in I/O managementCPU interacts with an I/O Controller
• Contains a set of registers that can be read andwritten
Processors access registers in two ways:
• Special I/O instructions: in/out instructions
• Memory mapped I/O: load/store instructions - 19What is a device driver?device-specific code in the
kernel that interacts directly with the device
hardware
Supports a standard, internal interface - 20What are the functions of memory managementOptimise use of RAM
Keep track of memory (what programs, available space
Allocated memory to programs to be loaded
De-allocate a program's memory space upon program completiion
Implemented with virtual memory - 21How do you acheive multitasking>Keep process information (context)
Choose the process to run ina fair and efficient way (scheduing algorithm)
Allocate CPU to a process (dispatching) - 22State the 3 ways to acheive multtaskingI/O break
Time-slicing
Scheduler - 23What is I/O break?• While one program is waiting for I/O to take place, another program is using the CPU to execute instructions.
- 24What is time-slicing?The CPU may be switched rapidly back and forth between different programs
- 25What is scheduler?Activated by I/O operation or real time clock interrupt
• Select next process to run
• Allocate CPU to the selected process - 26Whats a process?A program together with all the resources that are associated with it as it is executed
- 27What is I/O bound process?spends more time doing I/O than
computations, many short CPU bursts - 28What are CPU-bound processes– spends more time doing computations; few
very long CPU bursts - 29What is a process control block?Information associated with each process:
Process state
Program counter
CPU registers
CPU scheduling information
Memory-management information
Accounting information
I/O status information - 30What is the context switch?when CPU switches to another process,
the system must save the state of the old process and load
the saved state for the new process - 31What is the dispatcher?the module that gives control of the CPU to the process selected by the scheduler
- 32What is the job queueSet of all processes in the system
- 33What is the ready queue?set of all processes residing in
main memory, ready and waiting to execute - 34What is the device queueset of processes waiting for
an I/O device - 35What is the long-term scheduler/ job scheduler?select which process should be brought into the ready
queue;
invoked very infrequently (seconds, minutes) ⇒ may
be slow;
Controls the degree of multiprogramming; - 36What is the short-term scheduler/ CPU scheduler?selects which process should be executed next and
allocates CPU;
invoked very frequently (milliseconds) ⇒ must be fast - 37What are the scheduling algorithms's process selection policy?(3) First-Come, First-Served (FCFS) scheduling
Priority scheduling
Round-Robin (RR) Scheduling - 38What is FCFS scheduling?First-Come, First-Served (FCFS) scheduling:
• The process that request the CPU first is allocated CPU first
• Average waiting time is often quite long - 39What is priority scheduling?• Job with the highest priority is selected
• Priority is associated with each process, and the CPU is allocated to the process with the highest priority.
• Equal-priority processes are scheduled in FCFS order.
• No agreement on whether 0 is the highest or lowest priority. We assume that low numbers represent high
priority here. - 40What is a problem with priority scheduling?Indefinite blocking or starvation?
- 41What is round-robin scheduling?Time quantum is defined.
(10 to 100 milliseconds in lengths)
• Ready queue is treated a FIFO queue of processes. New processes are added to ready queue, sets a timer to interrupt after 1 time quantum, and dispatches the process
• CPU scheduler goes around the ready queue, allocating CPU to each process for a time interval of up to 1 time
quantum
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- Computer Science Flashcards on Introduction to Computer Systems: Lecture 8 Operating Systems, created by Nisha K on 10/01/2018.
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